how to type define a zip function in typescript

Question

Say I want to create a zip function:

function zip(arrays){
    // assume more than 1 array is given and all arrays 
    // share the same length
    const len = arrays[0].length;
    const toReturn = new Array(len);
    for (let i = 0; i < len; i++){
        toReturn[i] = arrays.map(array=>array[i]);
    }
    return toReturn;
}

console.log(zip([
    [1,2,3],
    [4,5,6],
    [7,8,9],
    [10,11,12],
]));
/*
Output:
(3) [Array(4), Array(4), Array(4)]
0: (4) [1, 4, 7, 10]
1: (4) [2, 5, 8, 11]
2: (4) [3, 6, 9, 12]
*/

In order to type define this function when all arrays hold the same type of elements:

    function zip<T>(arrays: T[][]): T[][]{/* codes omited here */}

However, when arrays are of different types of elements, I get confused about how to use generic type to finish the type definition.

    const zipedResult = zip([[1,2,3],[true,false,true],['a','b','c']]);
    // error raises: Type 'false' is not assignable to type 'number'.(2322)

what I want is

    [[1,2,3],[true,false,true],['a','b','c']]

could be automatically infered as (number|boolean|string)[][] without writing as (number|boolean|string)[][] or EVEN infered as [number[],boolean[],string[]] and result of zip infered as [number, boolean, string][]

How should I correctly type define zip to fullfill such features?

Answer 1

Here is an implementation that works for me:

export function zip<T extends unknown[][]>(
  ...args: T
): { [K in keyof T]: T[K] extends (infer V)[] ? V : never }[] {
  const minLength = Math.min(...args.map((arr) => arr.length));
  // @ts-expect-error This is too much for ts
  return range(minLength).map((i) => args.map((arr) => arr[i]));
}

for example zip(["x", "y", "z"], [true, false, true]) has inferred type [string, boolean][]